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La Serena, Chile

Ribeiro T.,SOAR Telescope | Ribeiro T.,Federal University of Santa Catarina | Baptista R.,Federal University of Santa Catarina | Kafka S.,Carnegie Institution of Washington
Astronomical Journal | Year: 2011

We present a multi-epoch time-resolved high-resolution optical spectroscopy study of the short-period (P orb = 11.2 hr) eclipsing M0V+M5V RS CVn binary V405 Andromeda. By means of indirect imaging techniques, namely Doppler imaging, we study the surface activity features of the M0V component of the system. A modified version of a Doppler imaging code, which takes into account the tidal distortion of the surface of the star, is applied to the multi-epoch data set in order to provide indirect images of the stellar surface. The multi-epoch surface brightness distributions show a low intensity "belt" of spots at latitudes ±40° and a noticeable absence of high latitude features or polar spots on the primary star of V405 Andromeda. They also reveal slow evolution of the spot distribution over ∼4 yr. An entropy landscape procedure is used in order to find the set of binary parameters that lead to the smoothest surface brightness distributions. As a result, we find M 1 = 0.51 ± 0.03 M ⊙, M 2 = 0.21 0.01 M ⊙, R 1 = 0.71 ± 0.01 R ⊙, and an inclination i = 65° ± 1°. The resulting systemic velocity is distinct for different epochs, raising the possibility of the existence of a third body in the system. © 2011. The American Astronomical Society. All rights reserved.

Armond T.,SOAR Telescope | Reipurth B.,University of Hawaii at Manoa | Bally J.,University of Colorado at Boulder | Aspin C.,University of Hawaii at Manoa
Astronomy and Astrophysics | Year: 2011

We present an optical/infrared study of the dense molecular cloud, L935, dubbed "The Gulf of Mexico", which separates the North America and the Pelican nebulae, and we demonstrate that this area is a very active star forming region. A wide-field imaging study with interference filters has revealed 35 new Herbig-Haro objects in the Gulf of Mexico. A grism survey has identified 41 Hα emission-line stars, 30 of them new. A small cluster of partly embedded pre-main sequence stars is located around the known LkHα 185-189 group of stars, which includes the recently erupting FUor HBC 722. © 2011 ESO.

Kepler S.O.,Federal University of Rio Grande do Sul | Pelisoli I.,Federal University of Rio Grande do Sul | Jordan S.,University of Heidelberg | Kleinman S.J.,Gemini Observatory | And 11 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2013

To obtain better statistics on the occurrence of magnetism among white dwarfs, we searched the spectra of the hydrogen atmosphere white dwarf stars (DAs) in the Data Release 7 of the Sloan Digital Sky Survey (SDSS) for Zeeman splittings and estimated the magnetic fields. We found 521 DAs with detectable Zeeman splittings, with fields in the range from around 1 to 733 MG, which amounts to 4 per cent of all DAs observed. As the SDSS spectra have low signal-to-noise ratios, we carefully investigated by simulations with theoretical spectra how reliable our detection of magnetic field was. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.

Schirmer M.,Gemini Observatory | Schirmer M.,University of Bonn | Diaz R.,Gemini Observatory | Diaz R.,CONICET | And 3 more authors.
Astrophysical Journal | Year: 2013

We report the discovery of Seyfert-2 galaxies in SDSS-DR8 with galaxy-wide, ultraluminous narrow-line regions (NLRs) at redshifts z = 0.2-0.6. With a space density of 4.4 Gpc-3 at z ∼ 0.3, these "green beans" (GBs) are amongst the rarest objects in the universe. We are witnessing an exceptional and/or short-lived phenomenon in the life cycle of active galactic nuclei (AGNs). The main focus of this paper is on a detailed analysis of the GB prototype galaxy J2240-0927 (z = 0.326). Its NLR extends over 26 × 44 kpc and is surrounded by an extended NLR. With a total [O III] λ5008 luminosity of (5.7 ± 0.9) × 1043 erg s-1, this is one of the most luminous NLRs known around any type-2 galaxy. Using VLT/XSHOOTER, we show that the NLR is powered by an AGN, and we derive resolved extinction, density, and ionization maps. Gas kinematics is disturbed on a global scale, and high-velocity outflows are absent or faint. This NLR is unlike any other NLR or extended emission line region known. Spectroscopy with Gemini/GMOS reveals extended, high-luminosity [O III] emission also in other GBs. WISE 24 μm luminosities are 5-50 times lower than predicted by the [O III] fluxes, suggesting that the NLRs reflect earlier, very active quasar states that have strongly subsided in less than a galaxy's light-crossing time. These light echoes, or ionization echoes, are about 100 times more luminous than any other such echo known to date. X-ray data are needed for photoionization modeling and to verify the light echoes. © 2013 The American Astronomical Society. All rights reserved.

Warner M.,Cerro Tololo Inter American Observatory | Heathcote S.,SOAR Telescope | Schumacher G.,Cerro Tololo Inter American Observatory | Cantarutti R.,Cerro Tololo Inter American Observatory | Parkes E.,Cerro Tololo Inter American Observatory
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

The SOAR telescope fast tip-tilt tertiary mirror, was delivered by the Goodrich Optical and Space Systems Division, Danbury, CT, and integrated into the SOAR optical system in 20041,2. It consist of a plane, light weighted 655×470 mm elliptical mirror, controllable over a range of ±1 mrad, in two axes, with a required position loop bandwidth of 50 Hz. It operates using the signal from a fast read-out guide camera to generate position commands, in an outer loop fashion. The original tertiary mirror controller consisted of several analog circuit boards, incorporating the position control loop compensation, and power amplifiers. This system was limited by the difficulty of making any modifications, to optimize the control loop, and meet the required bandwidth. The analog controller was replaced with a digital controller based on a National Instruments Compact RIO/FPGA device. This allows the full optimization of the control system, and also allows closing the torque (acceleration) loop using the optical feedback of the guide signal alone, which should result in even higher performance. This paper will describe the models, design, and performance tests, of the new digital control system. © 2010 SPIE.

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